The present invention relates to an antenna device used in high-frequency radio apparatuses and a compact-size high-frequency radio apparatus which uses the antenna device, and in particular, to a very compact-size high-frequency radio apparatus such as a watch-shaped high-frequency radio apparatus and an antenna device used in high-frequency radio apparatuses.
Conventionally, a helical dipole antenna is generally used as an antenna for portable devices such as cellular phones which belongs to high-frequency radio apparatuses.
The helical dipole antenna is configured in a manner that it is drawn out from or kept contained into the case of a portable device when used.
Furthermore, as disclosed in Japanese Patent Laid-Open Publication No.3-175826, there is also known another configuration in which another type of antenna is disposed within the case of a portable device so as to form a diversity together with a helical dipole antenna. As such an antenna for high-frequency radio apparatuses, which is incorporated within the case, an inverted-F antenna has been used.
A thin card type portable apparatus for 2.4[GHz] band employs a chip antenna using ceramic material.
However, the above-stated helical dipole is still large to apparatuses such as watch-size portable apparatuses which are demanded to be more compact. It is difficult to simply incorporate the helical dipole antenna into the apparatus case.
The degree of freedom for arrangement is low in the inverted-F antenna, since both its antenna element and its ground plate (main plate) are formed as an integral unit. As a result, the inverted-F antenna is difficult to be made compact any more.
On the other hand, in the case of the ceramic chip antenna, although the chip antenna itself can be surface-mounted, an antenna including its peripheral circuit is still large as a part. In addition, the chip antenna is fairly high in cost.
An object of the present invention is therefore to provide an antenna device for a high-frequency radio apparatus, a high-frequency radio apparatus, and a watch-shaped radio apparatus, which can be made more compact, increase sensitivity of the apparatus, and be prevented from being damaged by static electricity.
According to one aspect of the invention, an antenna device for a high-frequency radio apparatus is provided. The antenna device is connected to both a ground pattern and a feeding point formed on a circuit substrate. The antenna device comprises a metal, L-shaped antenna element, one end of which is connected to the ground pattern; and a feeding line, one end of which is connected to the feeding point and the other end of which is connected to a selected position on the antenna element so as to give the antenna device a predetermined value of impedance.
In another aspect, an orthogonal projection of the antenna element onto the plane defined in part by the ground pattern is included within the area of the ground pattern.
In another aspect, the area of orthogonal projection of the antenna element onto the plane defined in part by the ground pattern is smaller than the area of the ground pattern.
In another aspect, the antenna element is shaped into a lead wire.
In another aspect, the antenna device further comprises a dielectric member provided in the vicinity of the antenna element so as to set a resonance frequency of the antenna device to a predetermined value.
In another aspect, the dielectric member also functions to secure a display device, a circuit substrate, and a battery of the high-frequency radio apparatus.
In another aspect, a length of the antenna element is one fourth of the wavelength of the frequency to be used.
According to another aspect of the invention, a high-frequency radio apparatus is provided which comprises an antenna device for the high-frequency radio apparatus. The antenna devices comprises a ground pattern; a feeding point; a metal, L-shaped antenna element, one end of which is connected to the ground pattern; and a feeding line, one end of which is connected to the feeding point and the other end of which is connected to a selected position on the antenna element so as to give the antenna device a predetermined value of impedance; wherein the antenna device is connected to both the ground pattern and the feeding point formed on a circuit substrate. The high-frequency radio apparatus further comprises a plurality of electrical circuits mounted on the circuit substrate; and a display device for displaying information, the display device being positioned one side of the circuit substrate; wherein the antenna device is positioned on the same side of the circuit substrate as the display device.
In another aspect, the high-frequency radio apparatus further comprises a case which comprises a case body containing the antenna device, the display device, and the circuit substrate; and a case back made of conductive material. the high-frequency radio apparatus further comprises a battery having a plurality of electrodes for supplying power to drive the high-frequency radio apparatus; wherein the case back is electrically connected to either a ground pattern of the circuit substrate or the electrode of the battery.
According to another aspect of the invention, an antenna device for a high-frequency radio apparatus is provided. The antenna device is connected to both a ground pattern and a feeding point defined by an area formed on at least one layer of a multi-layer circuit substrate. The antenna device comprises a metal, L-shaped antenna element, one end of which is connected to the ground pattern; and a feeding line, one end of which is connected to the feeding point and the other end of which is connected to a selected position on the antenna element so as to give the antenna device a predetermined value of impedance.
In another aspect, an orthogonal projection of the antenna element onto the plane defined in part by the ground pattern is included within the area of the ground pattern.
In another aspect, the area of orthogonal projection of the antenna element onto the plane defined in part by the ground pattern is smaller than the area of the ground pattern.
In another aspect, the antenna element is shaped into a lead wire.
In another aspect, the antenna device further comprises a dielectric member provided in the vicinity of the antenna element so as to set a resonance frequency of the antenna device to a predetermined value.
In another aspect, the dielectric member also functions to secure a display device, a circuit substrate, and a battery of the high-frequency radio apparatus.
In another aspect, a length of the antenna element is one fourth of the wavelength of the frequency to be used.
According to another aspect of the invention, a high-frequency radio apparatus is provided which comprises an antenna device for a high-frequency radio apparatus. The antenna devices comprises a ground pattern; a feeding point; a metal, L-shaped antenna element, one end of which is connected to the ground pattern; and a feeding line, one end of which is connected to the feeding point and the other end of which is connected to a selected position on the antenna element so as to give the antenna device a predetermined value of impedance; wherein the antenna device is connected to both the ground pattern and the feeding point defined by an area formed on at least one layer of a multi-layer circuit substrate. The high-frequency radio apparatus further comprises a plurality of electrical circuits mounted on the circuit substrate; and a display device for displaying information, the display device being positioned on one side of the circuit substrate; wherein the antenna device is positioned on the same side of the circuit substrate as the display device.
In another aspect, the high-frequency radio apparatus further comprises a case comprising a case body containing the antenna device, the display device; and the circuit substrate; and a case back, made of conductive material. The high-frequency radio apparatus further comprises a battery for supplying power to drive the high-frequency radio apparatus; wherein the case back is electrically connected to either the ground pattern of the circuit substrate or an electrode of the battery.
According to another aspect of the invention, an antenna device for a high-frequency radio apparatus is provided, which comprises a circuit substrate with a ground pattern and a feeding point; a metal, L-shaped antenna element, one end of which is connected to the ground pattern; and a feeding line, one end of which is connected to the feeding point and the other end of which is connected to the ground pattern; wherein the antenna device is connected to both the ground pattern and the feeding point.
In another aspect, the circuit substrate has a plurality of layers, the feeding point and the ground pattern are formed on at least one layer of the plurality of layers, and the ground pattern covers approximately the entire surface of the layer on which the ground pattern is formed.
In another aspect, the ground pattern comprises an electrode pattern formed on a surface of the circuit substrate.
In another aspect, the ground pattern is formed over approximately the entire surface of the circuit substrate and is positioned under the antenna element.
In another aspect, a length of the antenna element is one fourth of the wavelength of the frequency to be used.
According to another aspect of the invention, a high-frequency radio apparatus is provided which comprises a wristwatch-shaped case; and an antenna device for a high-frequency radio apparatus. The antenna devices comprises a circuit substrate with a ground pattern and a feeding point; a metal, L-shaped antenna element, one end of which is connected to the ground pattern; and a feeding line, one end of which is connected to the feeding point and the other end of which is connected to the ground pattern; wherein the antenna device for the high-frequency radio apparatus is positioned within the wristwatch-shaped case, the antenna device being connected to both the ground pattern and the feeding point.
In another aspect, the circuit substrate has a plurality of layers, the feeding point and the ground pattern are formed on at least one layer of the plurality of layers, and the ground pattern covers approximately the entire surface of the layer on which the ground pattern is formed.
According to another aspect of the invention, an antenna device for a high-frequency radio apparatus is provided which comprises a circuit substrate having a ground pattern and a feeding point; a metal, L-shaped antenna element, one end of which is electrically connected to the ground pattern; and a feeding line, one end of which is connected to the ground pattern and the other end of which is connected to the feeding point, the feeding line extending from the circuit substrate.
In another aspect, the antenna element is made of a metal material and connected to the ground pattern via a conductive member made of the same material as the antenna element, the antenna element and the conductive member being integrally formed into an L-shape.
According to another aspect of the invention, a watch-shaped radio apparatus is provided which comprises a case and an antenna device for a high-frequency radio apparatus. The antenna device comprises a circuit substrate having a ground pattern positioned within the case; an antenna element, one end of which is electrically connected to the ground pattern, the antenna element extending from the circuit substrate and being in contact with an upper surface of the case; and a feeding line, one end of which is connected to the ground pattern and the other end of which is connected to a feeding point, the feeding line extending from the circuit substrate. The watch-shaped radio apparatus further comprises a radio circuit formed on the circuit substrate, the radio circuit being connected to the antenna device, wherein the case has a shape of a wristwatch and contains both the antenna device and the circuit substrate.